Fryers are widely used in restaurants for cooking a variety of food products such as French fries, fried chicken, chicken nuggets, fried fish, and the like. A typical fryer includes one or more fryer vats containing cooking oil, each vat having a burner or heating element for heating the oil to cooking temperature. Typically, the vat is adapted to receive a fry basket containing food products so that the food products can be immersed in the hot oil and cooked, and then removed, drained of excess oil and served. During cooking, the food products absorb an amount of oil. The absorbed oil, or uptake oil, is compensated for by periodically adding replacement or make-up oil to the vat for cooking subsequent batches of food.
In the course of cooking food products by frying, the oil becomes contaminated with particulate food matter and other debris. Over time, the cooking process causes increased degradation of the oil due to increases in the amount of impurities that accumulate in the oil, such as for example, increased levels of free fatty acids and total polar compounds in the oil. Additionally, the cooking oil degrades over a period of time due to being subjected to an elevated cooking temperature. The oil may also absorb flavors and odors from the food products, especially when cooking a strongly-flavored food such as fish. When continuing to cook with degraded vat oil an undesirable off-flavor is imparted to the food products affecting the quality of the cooked food product. Most significantly, the taste and texture of the final food product drops below acceptable quality standards. Thus, for optimum food quality it is necessary to periodically replace the oil in the fryer vat with fresh oil. The combined cost of the replacement oil and the discarded oil for commercial restaurant frying operations can account for a significant percentage of total cost of the cooked food product. Another cost consideration regarding oil usage is that oil changes are labor intensive and thus constitute a time-consuming and expensive operation.
To extend the useful life of the cooking oil and reduce the need for oil changes, which are time-consuming and expensive, it is known to filter the particulate matter from the oil. A conventional approach is batch filtration, in which the cooking oil is drained from the vat and then manually filtered before being returned to the vat. After the vat is drained, it may also be wiped out manually to remove any debris that may have accumulated in the bottom of the vat. This method has several disadvantages. First, the vat must be taken out of service and then the vat must be completely drained. Once the oil has been filtered and returned to the vat, it then must be reheated to cooking temperature. This is time-consuming and inefficient and, as a practical matter, has meant that the oil can only be filtered after the end of the business day at the restaurant. Moreover, manually filtering the oil tends to be a messy and inconvenient task.
To address these disadvantages, semi-automatic filtration methods have been proposed. These methods eliminate manual filtering by providing an oil outlet through which used oil is directed from the vat to a filter and a pump or other means for returning filtered oil to the fryer vat. Typically, the number of batches of food products is counted, and when a predetermined number of batches is reached, the oil is filtered. However, depending on the type of food product being cooked, the temperature of the oil and other factors, the number of batches by itself may not provide an accurate indication of whether the oil needs to be filtered. As food is cooked in hot oil, the oil degrades due to increasing levels of free fatty acids and total polar compounds. Using only the batch count, the oil might for example be filtered only once a day if a relatively small number of batches were cooked that day, but other factors may adversely affect oil quality, so that if the oil is not filtered more often, food product quality may suffer. Also, as a practical matter, restaurant personnel may choose to perform semi-automatic filtering only at the end of the business day, which may also result in food product quality degradation between filter cycles.
A need therefore exists for an improved device and method for automatically filtering cooking oil in a fryer.
In addition, a need exists for a system and method for monitoring the elapsed time since the last filtration of cooking oil in a fryer in addition to the number of batches or quantity of food products cooked, and automatically filtering the oil based on the elapsed time since the last filtration and batch or quantity count.
A need also exists for reducing the amount of oil usage for frying food product to reduce oil usage costs and labor associated with conducting a vat oil change.